COPYING: create a new file with points to the Kernel license files
With the addition of SPDX patchset, the contents of COPYING file
is now duplicated at two other files under LICENSE:
LICENSES/preferred/GPL-2.0
LICENSES/exceptions/Linux-syscall-note
It is easy to check that the contents of the licence written on
those files are identical with COPYING using:
Also, a new file was added, with describes how SPDX should work at
the Kernel source files:
Documentation/process/license-rules.rst
Instead fo having it copying the contents of two files, and not
even mentioning the third one, replace it by a file whose content
points to the other tree files, preserving the Kernel's license.
Adjust license-rules.rst accordingly.
Please notice that this file preserves the Kernel license as
is, without any changes.